UK patent No. 981,850 discloses as oil additives esters of polyisobutenylsuccinic acids which are obtained by reaction of polyisobutenylsuccinic acids with a polyol, e.g. pentaerythritol. These products have are known dispersant additives for lubricating oils, and are often referred to as "ashless" because of the absence of a metal component.
It has now been found that by using a particular class of polyols it is possible to prepare polyolefin-substituted dicarboxylic acid or anhydride ester derivatives having improved dispersancy properties when compared with the conventional ester derivatives described hereinabove.